Circuit breaker



R. W. SMITH CIRCUIT BREAKER Aug. 10, 1937.

Filed Jan. 29, 1937 E 1 ull F. tented Aug. 10, 1937 PATENT OFFICE CIRCUIT BREAKER Robert W. Smith, Coilingdale, Pa., assignor to General Electric Company, a corporation of New York Application January 29, 1937, Serial No. 122,950

8 Claims.

My invention relates to current responsive release devices for circuit breakers, more particularly to combined thermal and magnetic release devices for effecting automatic operation of a circuit breaker in response to predetermined current conditions and has for an object the provision of a simple, reliable, and inexpensive release device of this character.

Combined thermal and magnetic means have heretofore been provided for operating automatic circuit breakers either with a time delay in response to prolonged overloads or substantially instantaneously in response to short circuit conditions. In some cases, independent thermal devices and magnetic devices have been provided arranged to operate a common tripping member, but such arrangements are necessarily somewhat complicated and in many instances the space limitations prohibit the use of 5 separate devices. Combined thermal and magnetic arrangements have also been proposed in which the magnetic means forcibly bends the thermal element upon the occurrence of short circuit conditions and it will be apparent that this repeated bending of the thermal element by the magnetic means may seriously affect the calibration of the thermal element.

Accordingly, something is yet to be desired in combined thermal and magnetic release devices of this character and it is a further object of my invention to provide a compact and simple release device in which the magnetic means operates independently of the thermal means without subjecting the thermal element to excessive bending forces.

In carrying outmy invention in one form, I provide apivoted armature for releasing the circuit breaker tripping means, together with electromagnetic means for quickly operating the ar- 40 mature about its pivot to release the tripping means in response to predetermined current conditions and thermal means for bodily moving the armature and its pivot to release the tripping means with a time delay in response to other pre- 45 determined current conditions.

More specifically, the thermal means comprises a pair of bimetallic strips, the free ends of which are connected together by a conducting crossbar on which is pivotally supported the magnetiz- 50 able armature. The armature is biased for movement about its pivot and is restrained in predetermined relation to the bimetallic strips by adjustable stop means. Accordingly, fiexure of the bimetallic strips effects bodily movement of the 55 armature and its pivot, and electromagnetic means are provided for pivotally operating the armature against its bias independently of the bimetallic strips. Adjustment of the adjustable stop means is effective to vary simultaneously the time current setting of the thermal means and 6 the instantaneous current setting of the electromagnetic means.

For a more complete understanding of my invention, reference should now be had to the drawing in which Fig. 1 is an elevational view, 10 partly in section, of a circuit breaker provided with thermal release devices embodying my invention; and Fig. 2 is a somewhat diagrammatic view in skeleton perspective of the circuit breaker shown in Fig. 1. 15

Referring now to the drawing, I have shown my invention in one form as applied to a combined thermal and magnetic release device ID in connection with a three-pole circuit breaker ll of the type fully described in a copending applio cation of Joseph W. Seaman Serial No. 78,179, filed May 6, 1936, entitled Circuit breakers", which application became Patent No. 2,067,792 on January 12, 1937, assigned to the same assignee as the present invention. As will be more 25 fully described hereinafter, the tripping means for the circuit breaker ll includes a rotatable trip shaft l2 provided with a plurality of radially extending operating arms l3, the operating arms for the two outer poles of the circuit breaker be- :0 ing formed of suitable insulating material.

As shown best in Fig. 2, one of the combined thermal and magnetic release devices l0 embodying my invention is associated with each of the operating arms l3 and since these devices are identical in construction, only one will be described in detail. Each release device comprises a pair of spaced bimetallic strips l4 supported at their adjacent lower ends on suitable high resistance shunts l5 and IS, the shunt 15 being supported on a conductor bar I! extending along the base of the circuit breaker (Fig. 1) and the shunt l6 being connected by means of a flexible conductor Hi to the associated movable contact I9. As shown somewhat diagrammatically in Fig. 2, each of the movable contacts i9 is arranged abuttingly to engage a cooperating fixed contact 20, the fixed contacts 20 being connected by suitable leads 2| to terminal members (not shown).

Extending across the free upper ends of the bimetallic strips I 4 in bridging relation and secured thereto by means of suitable rivets 22 is a supporting member 23 formed of suitable conducting material. As shown in Fig. 1, suitable 2 washers 24 may be interposed between the crossbar 23 and the bimetallic strips M, if desired. It

will thus be apparent that the circuit through each pole of the circuit breaker maybe traced 5 from an external terminal screw 25 (Fig. l) by way of the conductor bar H to the release device i8 where the current divides, a portion of the current flowing throughthe bimetallic strips and the cross-bar 23 in -series to the flexible conductor 8 and the remaining portion of the current flowing directly through the high resistance shunts I5 and I6 to the flexible conductor l8. From the flexible conductor |8 the current, of course, flows through the circuit breaker contacts I9 and 28 andthe' conductor 2| to the other terminal (not shown).

Extending outwardly from the opposite edges of the cross-bar 23 I provide a'pair of arms 26 which support at their outer ends a pivot pin 2'! on which is pivotally mounted a magnetizable armature 28. This armature 28 is normally biased for clockwise movement about the pivot pin 21 by a coil spring 29 which surrounds the pivot pin 21 (Fig. 2), and the armature is restrained in a predetermined position relative to the bimetallic strips M by a stop screw 80 which extends through and threadedly engages the armature 28 with its innermost end abuttingly engaging the cross-bar 23.

Y 30 Adjacent the lower ends of the bimetallic strips l4 and partially encircling the conductor bar H,

I- provide electromagnetic means comprising a U-shaped member 3| formed of magnetizable material and having sloping pole faces 32 arranged to cooperate with an angularly disposed portion 33, formed on the lower end of the armature 28,

so as pivotally to move the armature against the bias of the spring 29 whenever a current of predetermined magnitude flows through the conducm tor bar Adjustably secured to the upper end of the armature 28 is an abutment member 34 which is formed of insulating material and which is arranged to engage the associated operating arm l3 on the trip shaft l2 whenever the arma- 5 ture 28 is moved.

It will be apparent now that when a prolonged overload current of predetermined magnitude flows through the bimetallic strips i4, the strips will flex so that the free upper ends thereof move in a left- 50 hand direction and thereby! bodily move the armature 28 and the pivot pin 21 so that the abutment member 34 rotates the associated operating arm IS in a clockwise direction to release the circuit breaker tripping means, as will be more fully 55 described hereinafter. This movement of the armature 28 and the abutment member 34 is accomplished with a time delay which depends upon the magnitude of the current and upon the heating characteristics of the bimetallic strips I4.

60 It will be understood, of course, that current of such magnitude induces in the magnetizable member 3| a magnetic flux which tends to attract the lower end 33 of the armature 28. The air gap between the pole faces 32 and the portion 65 33 of the armature 28, and the force of the biasing spring 29 are so proportioned, however, that this magnetic flux is insufiicient to rotate the armature against its bias. Upon the occurrence of overload conditions of short-circuit magnitude,

70 however, the magnetic flux induced in the magnetizable member 3| is sufliciently great to attract the portion 33 of the armature 28 so that the armature is operated about its pivot against the bias of the spring 29 substantially instantaneous- 75 1y so as to efiect clockwise rotation of the operating arm i3 independently of the bimetallic strips I4.

Adjustment of the time current setting of the bimetallic strips l4 and of the instantaneous current setting of. the electromagnetic means may be accomplished simultaneously by rotating the adjustable stop 30 so as to move the upper end of the armature toward or away from the crossbar 23. It will be apparent that if the upper end of the armature 28 is moved closer to the crossbar 23, the abutment member 34 will be moved away from the operating arm l3 and accordingly a greater flexure of the bimetallic strips M will be necessary to effect rotation of the operating arm. Likewise, adjustment of the armature in this direction will increase the air gap between the portion 33 of the armature and the pole faces 32 of the magnetizable member 3| and accordingly a larger current must flow through the conductor bar to effect movement of the armature 28 about its pivot.

If it is desired to adjust only the instantaneous current setting of the electromagnetic means, the abutmentmember 34 may of course be ad: justed to compensate for the change in the position of the armature 28 due to rotation of the adjustable stop 38. Likewise, the current characteristic of the bimetallic strips |4 may be independently adjusted by substituting for the high resistance shunts 5 and I6 similar shunts having different resistivities, or by entirely eliminating the shunts l5 and i8.

In order to insure a complete understanding of my invention and its operation, the remainder of i the circuit breaker shown in Figs. 1 and 2 'will now be described. For the purpose of the present invention, the manual operating mechanism for each pole of the circuit breaker may be briefly described as comprising a pair of overcenter springs 35, the respective adjacent ends of which are connected to the opposite ends of a pin 35 which extends through a slot (not shown) in one end of the movable contact 9, the other ends of the springs 35 being connected to a pin 37, which, as shown in Fig. 1,-is supported on the free ends of a pair of levers 38, only one of which is shown, the opposite ends of these levers being pivotally mounted on a fixed pin 39. The pin 31 which supports the upper ends of the overcenter spring 35 extends through a slot (not shown) in an operating member 48 which is pivotally mounted on a pin 4| supported between the upper ends of the U-shaped frame 42. In Fig. 2, the levers 38 have been omitted in order to simplify the diagrammatic showing and the pins 31 are shown as carried directly by the operating members 48.

As shown in Fig. 2, the operating member 40 for the middle pole is provided with an insulated handle 43 and the operating members 48 of the three poles are connected together by means of an insulated cross-bar 44 so that movement of the handle 43 is effective to move all of the operating members 48.

Also pivoted on the fixed pin 4| of each operating mechanism is a pair of spaced parallel links 45 (Fig, 2) the lower adjacent ends of which engage the pin 36, the links 45 being connected together intermediate their ends by a cross member 46. In addition, the pivot pin 4| carries a tripping member 41 having an extending portion 48, Fig. 2, arranged to engage the cross member 46 so as to move the links 45 and the movable contact 9 whenever the tripping member 41 is rotated in a clockwise direction, as viewed in the drawing.

These tripping members 41 are biased for rotation in a clockwise direction by suitable tripping springs (not shown) and are normally restrained in the position shown in the drawing by means of an insulated cross-bar 49 which connects the tripping members 41 of the three poles together for simultaneous operation and which is provided with a latch finger 50 which carries at its extending end a roller i (Fig. 1) arranged to engage a shoulder 52 formed in an elongate slot 53 in a pivot latching member 54.

As is more fully described in the above referred to Seaman application, this latch member 54 is pivoted on a pin 55 adjacent its lower end and is provided at its upper free end with a latching portion 56 arranged normally to engage the periphery of the rotatable trip shaft l2 which is provided with a notch (not shown: through which this latching portion moves whenever the trip shaft i2 is rotated to a predetermined position.

It will now be apparent that whenever the insulated handle 43 is operated so as to move the springs overcenter relative to the pivot pin 4|, all of the movable contacts I9 will be operated with a snap action between open and closed circuit positions. It will likewise be apparent that whenever one or more of my improved release devices effect rotation of the shaft l2 the latch member 54 will be released for movement in a clockwise 30 direction about its pivot so that the roller 5| is released from the shoulder 52 for movement along the slot 53 thereby to permit movement of the tripping members 41 in a clockwise direction in accordance with their bias so as to operate the movable contacts I9 to their respective open circuit positions independently of the overcenter springs 35.

While I have shown a particular embodiment of my invention, it will be understood, of course, an that I do not wish to be limited thereto since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current responsive release device comprising a movable thermal element, an armature pivotally mounted on said element, means biasing 5'.) said armature for pivotal movement, means for restraining said armature in predetermined relation to said thermal element whereby movement of said thermal element effects bodily movement of said armature and its pivot, and electromagnetic means for pivotally moving said armature against its bias independently of said thermal element.

2. A current responsive release device comprising a bimetallic element having a free end, to an armature pivotally mounted on said free end of said bimetallic element, means biasing said armature for pivotal movement, stop means for restraining said armature in predetermined spaced relation to said free end whereby moveu; ment of said free end effects bodily movement of said armature and its pivot, and electromagnetic means for pivotally moving said armature against its bias independently of said bimetallic element.

3. A current responsive release device com- 70 prising a plurality of spaced bimetallic strips, a supporting member carried by the free ends of said strips, an armature pivotally mounted on said supporting member and biased for pivotal movement in one direction, stop means cooperating with said support and said armature normally to restrain said armature in a predetermined position relative to said bimetallic strips whereby flexure of said strips effects bodily movement of said armature and its pivot, and electromagnetic means for pivotally moving said armature against its bias independently of said himetallic strips.

4. A current responsive release device comprising a pair of bimetallic strips, means for supporting said strips in parallel spaced relation, a cross-bar formed of high conductivity material supported on the free ends of said bimetallic strips and forming an electrical and mechanical connection therebetween, an armature pivotally mounted on said cross-bar and biased for pivotal movement in one direction, stop means carried by said armature and engaging said cross-bar remote from the pivot point of said armature for restraining said armature in predetermined relation to said bimetallic strips whereby fiexure of said strips effects bodily movement of said armature and its pivot, and electromagnetic means for pivotally moving said armature against its bias independently of said bimetallic strips.

5. In a circuit breaker having normally latched tripping means operative when released to actuate the circuit breaker to open circuit position, the combination of a current responsive release device comprising a pivoted armature, electromagnetic means for quickly operating said armature about its pivot to release said tripping means in response to predetermined current conditions, and thermal means for bodily moving said armature and its pivot to release said tripping means with a time delay in response to other predetermined current conditions.

6. In a circuit breaker having normally latched tripping means operative when released to actuate the circuit breaker to open circuit position, the combination of a current responsive release device comprising a magnetizable armature, means including a thermal element for pivotally supporting said armature, and electromagnetic means for quickly operating said armature about its pivot to release said tripping means in response to predetermined current conditions, said thermal element in response to other predetermined current conditions effecting bodily movement of said armature and its pivot to release said tripping means with a time delay.

7. In a circuit breaker having normally latched tripping means operative when released to actuate the circuit breaker to open circuit position, the combination of a current responsive release device comprising a pair of bimetallic strips, means for supporting said strips in parallel spaced relation, a cross-bar formed of conducting material secured to the free ends of said strips, a magnetizable armature pivotally supported on said cross-bar, conducting means for connecting said bimetallic strips in circuit with the contacts of said circuit breaker whereby said bimetallic strips are heated to effect bodily movement of said armature and its pivot and thereby release said tripping means in response to predetermined current conditions, and electromagnetic means associated with said conductor means for quickly operating said armature about its pivot to release said tripping means independently of said bimetallic strips in response to other predetermined current conditions.

8. A current responsive release device comprising a thermal element operable with a time delay characteristic in response to predetermined current conditions, an armature pivotally mounted 4- aosa'ne on said thermal element, means biasing said armature for pivotal movement, adjustable stop means for restraining said armature in predetermined relation to said thermal element whereby movement of said thermal element effects bodily movement of said armature and its pivot, and electromagnetic means for instantaneously moving said armature about its pivot against its bias in response to other predetermined current conditions, adjustment of said stop means being effective to vary simultaneously the time-current setting of said thermal element and the instantaneous current setting of said electromagnetic 5 means.

ROBERT W. SMITH. 

